Presuppositional apologetics

Presuppositional apologetics is a form of Christian apologetics, largely Calvinist that asserts that the acceptance of the proposition "God exists" and the truth of the Christian Bible is necessary for making the world intelligible. Presuppositional apologetics usually hinges on the rejection of Thomist apologetics, which attempt to establish logical proofs for the existence of god. The Transcendental Argument for the existence of God (TAG) is often considered a claim of presuppositional apologetics.

There are generally two branches of presuppositional apologetics: Van Tillian presuppositionalism and Clarkian presuppositionalism, attributed to their namesakes, Cornelius Van Til and Gordon Clark.

Basic Forms and Principles

Van Tillian Presuppositionalism

Van Tillian presuppositionalists accept that the Bible is the arbiter of truth and error, and that all knowledge claims must be given Biblical justification. They cannot be known independently of the Bible. They often grant that certain statements generally accepted as "foundational" are true, they refuse the condition that such statements are "foundational". The only foundational presupposition is the truth of the Bible.

Skeptic: Is modus ponens the case?

VT Apologist: Of course modus ponens is the case. It is one of the most important rules of logic.

Skeptic: But isn't modus ponens, given its standing as a rule of logic, foundational?

VT Apologist: No. Only the Bible is foundational. Modus ponens can be used to check the coherence of other propositions with the truth of the Bible.

Van Tillian presuppositionalism also hinges on a distinction between proof and persuasion where there can be conclusive proofs of the existence of God that are not persuasive, because the skeptic rejects the epistemological framework necessary to those proofs.

Clarkian Presuppositionalism

Clark treated the truth of the Bible as the axiom of a logical system. Clarkian presuppositionalism then asserts that the worldview that results from the acceptance of the axiom can be tested for consistency and comprehensiveness. Clark is committed to the possibility of demonstrating that there are no discrepancies or contradictions which can be produced by accepting the Bible as true, and embraces the possibility of using formal logic as a method for testing the propositions in order to ensure this. This approach usually draws criticism from Van Tillian presuppositionalists, because they regard the use of formal logic that is being embraced as an eschewal of presuppositionalism, generally, as it seems to cede that logic is natural. Because Clark viewed the axioms of predicate logic, and Platonic epistemology, as fully derivable from the Bible, the issue is really one of establishing the consistency and coherence of the text, in order to ensure that all derivable propositions are non-contradictory.

Critiques

Critique form Un-Falsifiability

One critique of presuppositional apologetics is that it is committed to the claim "God exists" being true; however, because it asserts that the existence of God is necessary for any belief to be intelligible, it is not possible to falsify the claim. The exchange looks something like this:

Skeptic: What would have to be the case for you to reject the belief that God exist?

Apologist: There isn't anything, because my ability to know anything is conditioned on God existing in the first place. If there were conditions such that God didn't exist, then I wouldn't be able to comprehend God existing, or not existing, or any belief.

The move is a reversion to the belief being primitive. The concern is greater, though, when it comes to the belief about the truth of the Bible. If it is the case that the Bible makes claims which are empirically verifiable, and those claims are not verified upon investigation, then there are some serious concerns regarding whether the empirical methods are to be dispensed with. This is similar to the issue of whether the Bible produces logical contradictions; in Clarkian presuppositionalism, this is regarded as being a serious problem.

Critique from Modal Logic

One critique of presuppositional apologetics is that it makes a non-tautological existential claim (i.e. 'God exist') primitive. It is generally accepted, in logic, that only universal claims and tautological claims can be primitive.

In modal logic, existential claims about logical possibilities (like 'God exists') are generally believed to be true in at least one possible world and false in some other possible world. Because they are generally accepted as being false in some possible world, they are not considered necessary truths. Only necessary truths can be primitive.